Do phylogenetic trees change?
Yes. Phylogenetic trees change as the evidence we have changes and increases.
A phylogenetic tree is really a hypothesis, or 'best explanation' for how we think a group of species is related. The fossil record is not complete, there are always gaps, so scientists use the best evidence available at the time to show how those species are related.
A phylogenetic tree may change for example if new species are found, and have to be included, or if new evidence shows that the species already 'in the tree' are related differently from that shown.